Suppose Milk and Cereal Are Compliments and the Demand for Milk

Suppose milk and cereal are compliments and the demand for milk is Q^d_m = 40 - 6P_m - 2P_c,where Q^d_m stands for millions of gallons of milk demanded,P_m stands for the price of milk and P_c stands for the price of cereal.The supply of milk is Q^s_m = 6P_m - 8,where Q^s_m stands for millions of gallons of milk supplied.The demand and supply of cereal are Q^d_c = 90 - 5P_c - P_m and Q^s_c = 5P_c - 10,respectively,where Q^d_c stands for millions of boxes of cereal demanded and Q^s_c stands for millions of boxes of cereal supplied.Which of the following gives the price of milk in terms of the price of cereal?

A) P_m = 4 - (P_c/6)
B) P_m = (32/12) - (P_c/6)
C) P_m = (32 - 2P_c) /12
D) P_m = (32/12) + (P_c/6)